The present invention relates to warehouse storage arrangements and, more particularly, to storage racks having bays for receiving multiple loads.
It is common practice in warehouses to store goods at multiple levels using storage racks. Each rack defines an array of storage bays in horizontal and vertical rows. Typically, the racks are situated back-to-back with an aisle spacing each pair of racks, and each bay can receive only a single load of goods. More specifically, the goods are arranged on a pallet and a forklift truck is used to distribute the palletized loads to their desired storage locations.
It has been recognized that such warehousing arrangement wherein one aisle is required for each pair of racks, with each rack only one load deep, does not provide a particularly efficient use of floor space. To provide greater efficiency, storage racks have been proposed having greater depth so that loads can be stored at more than one location within each bay. One proposed storage rack is adapted to receive two loads of palleted goods through a front end, thereby essentially doubling the amount of storage area associated with each aisle. A first load of goods is placed upon a trolley in the storage bay, and the loaded trolley is moved rearwardly along a track to an inner or rear location when a second load is inserted into the same bay. The trolley, which is biased forward by resilient means, returns its load to the front location of the bay when the second load is removed. For further information regarding the structure and operation of this storage rack, reference may be made to U.S. Pat. No. 4,155,462.
In the system described in that patent, the weight of the second load prevents the forward return movement of the trolley until it is removed. It is recognized in the '462 patent that a light load in front of the trolley may be insufficient to prevent forward movement of the trolley; however, as the system is intended for use in warehouses of large capacity, this danger is dismissed as minimal. While the danger of a forward-biased trolley pushing a fully loaded pallet into the aisle may be minimal, such may not be the case when a pallet is nearly empty. In many warehouse facilities, goods will frequently be individually picked from a loaded pallet rather than withdrawn as an entire pallet load. If the load becomes sufficiently light, a forward-biased trolley may dislodge the pallet and shove it and the remaining goods into the aisle.
A recently proposed storage rack has bays which receive multiple loads through a front opening with the first-received load being movable on a trolley between a forward storage location and a rear storage location. Each bay has inclined rails, sloping downwardly toward the bay front end, so that the trolley is biased by the force of gravity toward its forward location. To retain the trolley at the rear location, releasably locking means are provided. With such storage rack, the pallet support surface of the trolley is not horizontal, but is disposed generally parallel to the trolley rails. A forklift truck operator after lifting a palletized load from the floor might not, for one reason or another, angle the pallet so that its engagement surface exactly matches that of the trolley support surface. Upon roughly setting the load on the trolley, the mismatch of surfaces could result in torque being applied to the trolley which could promote premature wear of rack and/or trolley components or, in an extreme situation, result in derailment of the trolley. Of course, the forklift operator could take the extra time required to angle the pallet so it matched the trolley support surface. This, however, reduces the operator's loading efficiency.
In another recently proposed storage rack, each bay also is adapted to receive multiple loads. Each bay is provided with one or more sets of rails which, while inclined, are all disposed at the same level. Up to three trolleys, the support surfaces of which are parallel to the rails, may be used in addition to a front platform so that a single bay may accommodate up to four loads. As the trolleys telescope, they are required to have legs of increasing height which limits the number of trolleys usable in a single bay. Furthermore, with this arrangement each trolley is required to roll on a different rail portion which makes difficult the provision of hold down means to retain the trolleys on their tracks in case a load might be dropped on a trolley thus applying torque which tends to lift the trolley wheels from their rails. For a further description of the structure and operation of this storage rack, reference may be made to U.S. Pat. No. 4,341,313.